RcTek : Information & Resources for the Model Car Racer

Two Speed Transmission Ball Bearing Adjusters Wear

This article is part of a section of the RcTek site that is devoted to informing the model car owner about the various different aspects of Transmissions.

This article covers a wear problem regarding the ball bearing adjusters/actuators used in the two speed transmissions of some model cars.

Ball Bearing Adjuster/Actuator Wear

After some considerable use, due to the amount of gear changes and the vibrations involved with IC (Internal Combustion) model cars, the ball bearing in the hollow adjusters can become trapped.

This problem can result in sticking gear changes or, in extreme cases, no gear changes at all.

Two Speed Transmission new adjusterTwo Speed Transmission worn adjuster

Two Speed Transmission assembly

In the diagram on the right you can see where the ball bearings (green) are in the two speed assembly. They provide a low resistance, free running contact point between the adapter and the shoes and sit just inside some specially made hollow grub screws (red).

As stated above, after a considerable amount of use, the ball bearings can, through pressure and vibration, move upwards and become trapped inside the hollow grub screws.

The two diagrams above show the ball bearing/grub screw assembly in greater detail. The one on the left is an example of a new assembly and the one on the right shows just what can happen when the grub screw wears and/or deforms and allows the ball bearing to move up and become trapped.

I must stress that this is a problem that would take a very long time to manifest itself into a problem that would affect the working of your two speed assembly. There would be some loss of adjustment, but this is not really a problem and this article only serves to warn you of what can happen.

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© 2001, 2009 by Darren Burnhill